Fire-resistant hydraulic fluid



United States Patent Oflfice Patented Oct. 11, 1966 3,278,442 FIRE-RESISTANT HYDRAULIC FLUID Alan Beerbower, Westfield, and Donald A. Pattison, Ro-

selle, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware N Drawing. Filed July 25, 1963, Ser. No. 297,674 8 Claims. (Cl. 252-75) This application is a continuation-in-part of application Serial No. 164,386, filed January 4, 1962 and now abandoned.

This invention relates to hydraulic fluids comprising stable water-in-oil emulsions of mineral oils. These emulsions are characterized by fire resistance, low pour point, low temperature pumpability, antirust properties, Wearreducing properties and emulsion stability.

There has been a need, particularly in the mining and metallurgical industries, for a hydraulic fluid for hydraulically operated equipment that will not present a fire hazard when leakage or line rupture exposes the fluid to high temperatures. Fire-resistant fluids are desirable in such locations as die-casting plants, glass-molding plants, steel mills and coal mines.

Among the types of fire-resistant fluids that are available are included: phosphate esters, mixtures of Water and glycols such as ethylene glycol, oil-in-Water, and water-inoil emulsions. The water-in-oil emulsion-type fluids are particularly desirable because of their lower cost and because of the ease of conversion from the use of conventional mineral oil hydraulic fluids to the emulsion-type fluids. There are a number of problems that arise, however, in the use of emulsion-type hydraulic fluids. One of these is that the emulsion tends to separate or migrate in storage. Migration is a phenomenon in which the emulsion tends to stratify into layers of different density and water content on standing. This of course is an undesirable property. Another problem is that emulsion-type fluids tend to promote greater wear of pump parts than is experienced with fluids in which the base is entirely mineral oil.

It is an object of the present invention to provide improved hydraulic fluids of the Water-in-oil type that are fire resistant, that have a minimum tendency to undergo water migration in storage, that resist separation in freezing-thawing cycles, that have desirably low pour points, that exhibit low temperature pumpability, and that reduce wear-promoting tendencies.

In accordance with the present invention, it has been found that a fire-resistant water-in-oil emulsion hydraulic fluid that possesses the above-recited properties can be prepared from a mixture of about 35 to 67 wt. percent of a low cold test mineral oil, from about 3 to about 10 wt. percent of an emulsifier package which is more explicitly defined hereinafter, and from about 30 to about 55% water, and preferably with smaller concentrations of auxiliary agents. Preferably for proper fire resistance, the emulsion should contain at least 40% water and the preferred range is 40 to 45 wt. percent of water.

The base oil may be any natural or synthetic mineral oil having a pour point no higher than 0 F., preferably F. or lower. Coastal naphthenic oils or properly dewaxed paraflinic oils may be used, for example. Preferably, the oil has a viscosity in the range of 75 to 200 SSU at 100 F.

The emulsifier package is made up of several (i.e. more than two) ingredients. The first of these is a metal, organo sulfonate having a molecular weight in the range of from about 300 to about 1200. These sulfonates are the alkali metal and alkaline earth metal sulfonates, e.g. Ca, Na, Ba, Li, Mg. etc. The sulfonate functions not only as an emulsifier but also as an antirust agent. The sulfonates are preferably the sodium and/or calcium salts of sulfonic acids obtained by sulfonating alkylated aromatic hydrocarbons such as those naturally occurring in naphthenic lubricating oils of 500-1200 SSU viscosity at F. Specific sulfonates include the salts of acids obtained in the manufacture of USP white oil, or synthetic sulfonate obtained from alkylated or cycloalkylated benzene or naphthalene of suitable molecular weight.

Sodium sulfonates used as water/ oil emulsifiers tend to make emulsions most stable as oil-in-water emulsions. Increasing the molecular weight of the sodium sulfonate tends to make the water-in-oil emulsions more stable. Unfortunately, when the sodium sulfonate molecular weight increases, a tendency of gelation is sometimes noted in the Water-free portion of the emulsion hydraulic fluid system. This gelation would not permit shipment of a waterfree concentrate to a fluid user to save freight charges. (The fluid user then adds water to make the emulsion.)

Calcium sulfonates used as water/oil emulsifiers tend to make emulsions most stable as Water-in-oil emulsions. However, freeze-thaw stability (cycling emulsions from room temperature to freezing conditions) of emulsions containing calcium sulfonate as a major emulsifier is poor. In accordance with the present invention it has been unexpecteclly found that a combination of calcium sulfonate and sodium sulfonate produces a superior emulsifier system. In such a system the weight ratio of sodium sulfonate to calcium sulfonate will be from about 1/1 to about 10/ 1 with a preferred ratio of about 5/1.

The second component of the emulsifier package is an alkoxylated aliphatic alcohol obtained by treating an aliphatic alcohol of 12 to 20 carbon atoms with from less than 1 mole to up to 4 moles of ethylene oxide or propylene oxide per mole of alcohol. Among the alkoxylated alcohols that may be used are a partially saturated alkoxylated tallow alcohol, an alkoxylated lauryl alcohol, an unsaturated alkoxylated oleyl alcohol, and an alkoxylated tridecyl alcohol. Several method for carrying out the oxyalkylation are illustrated in US. Patents 1,970,578 and 2,174,761.

Tallow alcohol is a mixed alcohol obtained by the hydrogenation of tallow. It is principally G -C alcohols with minor amounts of C C and C alcohols. The tridecyl alcohol may be a C oxo alcohol prepared by the well-known oxo process wherein an olefin is reacted with carbon monoxide and hydrogen in the presence of a suitable catalyst, usually cobalt. The reaction products are primarily aldehydes of one more carbon atom than the starting olefins. The aldehydes are converted to the corresponding alcohols in a separate hydrogenation step.

The lauryl alcohol may be the commercial mixture of saturated aliphatic alcohols known as Lorol, consisting mostly of C and C alcohols but having small proportions of C and C -C alcohols.

A third ingredient of the emulsifier package is a coupling agent, which is actually a supplementary emulsifier, selected on the two bases of creating a favorable hydrophilelipophile balance and of disordering the emulsifier monolayer. Thus, if the other emulsifiers are excessively oil soluble, a highly water-soluble ingredient is selected; and the shape of the molecule of the -coupling agent is chosen so as to prevent close packing of the molecules of the main emulsifiers. Usually the choice is made empirically', as emulsifier theory is not yet adequate for detailed mathematical predictions.

The coupling agent is preferably a hydr-oxy compound selected from the group consisting of glycols and glycol ethers of from 3 to 8 carbon atoms and aliphatic alcohols of from 3 to 20 carbon atoms. Specific coupling agents include diethylene glycol, propylene glycol, butyl carbitol, ethylene glycol monomethyl ether, tetramethylene glycol, ethylene glycol monobutyl ether, isopropanol, tridecyl alcohol, oleyl alcohol, and C oxo alcohol.

The composition of a two-component or three-component emulsifier package may range from about 35 to 90 wt. percent of sulfonate, 10 to 65 wt. percent of the alkoxylated alcohol, and from to 30% of the coupling agent.

A particularly useful four-component emulsifier package employs, in addition to the three above-described ingredients, about 0.2 to 1.0 wt. percent oleic acid. Oleic acid is well known as an antiwear agent and emulsifier. However, its elastomer swelling properties, especially on widely used elastomers such as Buna N (butadiene/acrylonitrile rubber) usually precludes its use as a hydraulic fluid additive.

While it may be omitted, it is preferred to include as an ingredient of the emulsion an antiwear agent, prefera'bly one that is stable in the presence of water at 190 F. for at least 1000 hours. Depending on the potency of the antiwear agent it may be present from 0.1 to about 10 wt. percent. A satisfactory antiwear agent is an ester of a C to C monohydric alcohol and a C to C fatty acid, such as methyl oleate which is employed in about wt. percent concentration in the finished emulsion. Related antiwear agents that may -be used include isopropyl oleate or other esters of low molecular weight monohydric alcohols and high molecular weight monobasic aliphatic acids. Specific alcohols include methyl, ethyl, isopropyl, secondary and tertiary butyl. Acids include oleic, lauric, ricinoleic, myristic and decanoic.

Other deirable ingredients include an antioxidant, preferably a phenolic material in concentrations of from about 0.05 to about 2 weight percent, a bactericide in concentrations of from about 0.01 to about 0.5 wt. percent and a vapor phase rust inhibitor in concentrations between about 0.01 and about 2 wt. percent. A particularly effective antioxidant is 2,6 di-tert. butyl-4-methyl phenol, which may be used in a concentration of about 0.5 wt. percent. Bis phenols such as 4,4'- methylene bis (2,6-di-tert.-butyl phenol) are also useful antioxidants. Other suitable antioxidants include, for example, phenyla-napht hylamine, phenyl- B-naphthylamine and butylated hydroxy anisole. A suitable bactericide is the sodium salt of dichlorophene, which may be obtained commercially under the name of Sindar G-4. Tris nitro, 2- nitro-2-methyl propane diol, and similar bactericides may also be used.

While the sulfonate component of the emulsifier does function as a rust-preventing agent, there is need for an additional rust inhibitor to prevent rusting in the vapor space of the pumps of the hydraulic system; hence, a vapor phase rust inhibitor is needed. Morpholine is a preferred inhibitor for this purpose, and can 'be used at about 0.03 to 0.13 wt. percent concentration. Cyclohexyl amine is also an effective vapor phase rust inhibitor. Other effective vapor phase rust inhibitors include ethylene diamine, amyl amine or similar volatile amine. Any volatile amine-type compound having a vapor pressure close to that of water may be used.

The nature of the invention, the manner in which it may be practiced, and the benefits derivable from the invention will be more fully understood when reference is made to the following examples.

EXAMPLE 1 The following is a general description of the method for manufacturing a concentrate which can later be converted to a water-in-oil emulsion suitable for use as a fireresistant hydraulic fluid.

A kettle is charged wit-h a suitable base oil together with emulsifiers and antioxidants. The mixture is heated to about 150 F. and blended for a period of 1 to 2 hours. After one hour the bactericide and rust inhibitor and any other minor ingredients employed are added. A sample of the blend is then taken and to it is added slowly the amount of water required to make a finished emulsion. Then, viscosity and centrifuge stability tests are run. Should the concentrate require rebalancing, either 0.5 wt. percent of sulfonate or 0.5 wt. percent of ethoxylated alcohol may be added. If neither of the above materials provides a good test emulsion the concentrate may be balanced by adding up to 0.5 wt. percent of diethylene glycol or other coupling agent" as previously disclosed.

If the concentrate is to be converted into a finished emulsion in the plant, the desired amount of water is added to the finished concentrate with good mixing during a period of 40 minutes and the mixture is stirred for an additional 30 minutes with maximum agitation. Care should be taken to avoid water Stratification; an excellent method is to use a bottom-drain pump-around circuit.

EXAMPLE 2 Using the general procedure of Example 1, three different emulsifiable concentrates and the corresponding finished emulsions were prepared wit-h ingredients set forth in Table I.

1 In each case consists of 57 wt. (60 vol. or the concentrate and 43 wt. (40 vol. of water.

Viscosity at 100 F. is 100 SUS.

2 Coastal naphthenic distillate oil. V.I. is about 26.

3 Concentrate in mineral oil containing 63 wt. sullonate 01 400- 500 mol. wt. (avg. 450) obtained in manufacture of white oil.

4 Concentrate in mineral oil containing 43-46 wt. sulfonate 01 880 avg. mol. wt.

fdProduct of treating 1 mole of tallow alcohol with 3 moles Methylene 0x1 e.

a Product of treating 1 mole of 013 0x0 alcohol with 1.5 moles of ethylene oxide.

lgroduet of treating 1 mole of oleyl alcohol with 2 moles of ethylene on e.

' 2,6-di-tcrt. butyl p-cresol.

40% aqueous solution of the sodium salt of dlchlorophen.

morpholine, 10% water.

EXAMPLE 3 Emulsions of Example 2 were subjected to a number of tests including centrifuge stability, flame resistance, freeze-thaw separation, and antiwear performance. The tests are described as follows:

Centrifuge stability test A 100 ml. sample of finished emulsion is centrifuged 70 minutes at 1500 r.p.m. in an ASTM D-9l apparatus. The bottom 9:0.3 grams are distilled in the ASTM D- apparatus. Good performance is shown by similarity between water content of bottom sample and bulk water content.

Flame resistance tests A fire-resistant hydraulic fluid must meet the requirements of Schedule 30, Subpart B, Bureau of Mines, United States Department of the Interior, published in the Federal Register, Sept. 25, 1959, page 7728. To simplify the work in comparing the competitive samples, only the room temperature pipe cleaner test, subparagraph 3 of paragraph (c) of Section 35.22 was run here. However, this is considered to be the most diflicult of the tests to pass, and normally a fluid will pass all of the other fire resistance tests if it will pass this one.

Freeze-thaw separation test A 100 ml. sample of the test emulsion is placed in a graduate, cooled to F. and then warmed to +77 F.

6 What is claimed is: 1. A water-in-oil emulsion adapted for use as a hydraulic fluid which comprises from about 30 to about 55 weight percent of Water, about 35 to about 67 Weight persix times. After these six cycles the graduate is stored 5 cent of a mineral lubrlcatmg 011, havmg a pour point no on a shelf 0?1 2 days, at which time separated 011 and/ or higher than F. and about 3 to about 10 Weight percent Water Is note A f of an emulsifier, said emulsifier consisting of a mixture mlwear per ormance of (a) about 35 to 90 weight percent of a metal organo The fluid under test y run in y or all Of the sulfonate, wherein said sulfonate has a molecular weight following pumps. For the present comparative tests the 10 of fr bout 300 to 1200 and is selected from the group first of those listed was used. consisting of alkali metal and alkaline earth metal sulfo- (a) Vickerssingle Stage g-P' pump, 1150 mates of alkylated aromatic hydrocarbons, (b) about 10 to po 1000 P- Cartridge is Weighed before 65 weight percent of a condensate of a C C aliphatic and after testing for component and total Wear loss. alcohol with about 1 to 4 moles of a C -C alkylene oxide (b) Vickers-two stage vane.l3.4 g.p. m. pump, 1150 15 per mole of alcohol and (c) 0 to about 30 weight perrpm. 400 p.s.i. I0 2000 p.s.i., 120 F. Pressure is regucent of a hydroxy compound selected from the group lated to run 5 seconds at 400 p.s.i.g., then 5 seconds at consisting of glycols and glycol ethers of from 3 t0 8 2000 p.s.i.g. for duration of test. Cartridges are evalucarbon atoms and aliphatic alcohols of from 3 to carated as above. bon atoms.

(c) Denisonmulti-piston.7.3 g.p.m. pump, 1150 20 2. The water-in-oil emulsion of claim 1 wherein said -p- 00 .s.i., 1 F- P r r v l d as a v fiuid contains as an additional ingredient, about 0.2 to

(d) Commercial shearing and stamping company.- 1.0 wt. percent olei a id, Gear type 14 gpm. pump, 1150 r.p.m., 1500 p.s.i., 160 3. The water-in-oil emulsion of claim 1 wherein said F. Visual examination only. water concentration is in the range of 40 to 45 weight Emulsions I and II were also compared in the above percent. tests with a number of commercially available emulsion- 4. The water-in-oil emulsion of claim 1 including as an type hydraulic fluids. The results of these tests are set additional ingredient from about 0.1 to about 10 weight forth in Table II. It will be seen from the results that percent of an antiwear agent consisting of an ester of a the emulsions of the present invention were superior to all C to C monohydric alcohol and a C to C fatty acid. of the commercially available materials in many of their 5. The Water-in-oil emulsion of claim 1 containing as properties, particularly in flame resistance, prevention of an additional ingredient from about 0.05 to about 2 wear, and separation on standing. weight percent of an antioxidant selected from the group Emulsion III was compared to Emulsions I and II and consisting of 2,6-di-tert. butyl-4-methyl phenol, 4,4 meth- Was found to be superior to the latter in low temperature ylene bis (2,6-di-tert.-butyl phenol), phenyl-a-naphthylpumpa'bility, pour point and pump wear. amine, phenyl-fl-naphthylamine and butylated hydroxy TABLE II Emulsions of Invention Competitive Commercial Emulsions I II A B o D E F G Inspections:

Gravity, APL 17. a 17. 3 17. 4 21.6 Pour Point, F +25 -10 5 0 Viscosity, SSU at 100 518 450 1,110 411 Weight Percent Water 43.0 43.0 41.7 43.0 Neut No., mg. KOI-I/gm,

ASTM D974 0. 05 0. 05 0. 53 Basic Test Results:

Centrifuge Stability, Percent H O in Bottom 10% 52. 2 44.0 67.0 57. 7 62. 2 32. 5 88 77. 2 ASIM D130 Copper Strip Cor rosion, 3 hrs. at 212 FJ 0+ 0 113 1A 1A Flame Resistance, Cycles to Burn at 77 F 44. 2 44. 2 42. 4 41. 4 24.8 32. 2 Freeze-Thaw Separation at 6 Cycles None None None None None None 2 19 7 3 43 Fluid Condition After 48 Hours at 185 F.:

Free Oil, Percent 5 0 30 50 20 Free H7O, Percent 0 0 0 3O 0 Relative Wear at 250 Hours in Vickers Single Stage Vane Pump 1.10 1. 00 3. 90 1. 22 1. 92 4.08 2.00 1. 22 2.08

1 Zero rating is equal to freshly polished strip; zero plus represents trace of tarnish.

2 Percent H 0. 3 Percent oil.

As shown in the examples, the hydraulic fluid of the anisole.

invention can be prepared as a concentrate for later mixing with water when the fluid is to be used. If the concentrate contains no antiwear agent it will range in composition from about 77 to about 96% oil and from about 4 to about 23 weight percent of emulsifier. If, as is preferred, it also contains the antiwear agent it will range in composition from about 56 to about 96% oil, from about 4 to about 23 weight percent of emulsifier and from about 0.2 to about 22 weight percent of antiwear agent.

The examples herein presented are :merely illustrative of the invention. There is no intent to limit the scope of the invention to those examples, nor is it to be limited by any theory regarding its mode of operation. Variations within the purview of the appended claims are contemplated.

6. The water-in-oil emulsion of claim 1 containing as an additional ingredient from about 0.01 to about 2 weight percent of a vapor phase rust inhibitor wherein said inhibitor is a volatile amine having a vapor pressure close to that of Water.

7. The water-in-oil emulsion of claim 1 wherein (a) is a mixture of sodium sulfonate and calcium sulfonate in a Weight ratio of from about 1/1 to about 10/ 1.

8. A concentrate, capable of dispersion in water to form a fire-resistant hydraulic fluid, which comprises from about 56 to about 96 weight percent of a mineral lubricating oil, having a pour point no higher than 0 F., from about 4 0t about 23 Weight percent of an emulsifier and from about 0.2 to about 22 weight percent of an antiwear agent, said emulsifier consisting of a mixture of (a) about 35 to about 90 weight percent of a metal organo sulfonate wherein said sulfonate has a molecular weight of from about 300 to about 1200 and is selected from the group consisting of alkali metal and alkaline earth metal sulfonates of alkylted aromatic hydrocarbons, from about 10 to 65 weight percent of a condensate of a C C aliphatic alcohol wit-h about 1 to 4 moles of a C -C alkylene oxide per mole of alcohol and from 0 to 30 weight percent of a hydroxy compound selected References Cited by the Examiner UNITED from the group consisting of glycols and glycol ethers of 10 LEON D. ROSDOL, Primary Examiner.

JULIUS GREENWALD, A. T. MEYERS, Examiners.

R. D. LOVERING, Assistant Examiner.

from 3 to 8 carbon atoms and aliphatic alcohols of from 3 to 20 carbon atoms, said antiwear agent consisting of an ester of a C to C weight monohydric alcohol and a C to C fatty acid. 

1. A WATER-IN-OIL EMULSION ADAPTED FOR USE AS A HYDRAULIC FLUID WHICH COMPRISES FROM ABOUT 30 TO ABOUT 55 WEIGHT PERCENT OF WATER, ABOUT 35 TO ABOUT 67 WEIGHT PERCENT OF A MINERAL LUBRICATING OIL, HAVING A POUR POINT NO HIGHER THAN 0.*F. AND ABOUT 3 TO ABOUT 10 WEIGHT PERCENT OF AN EMULSIFIER, SAID EMULSIFIER CONSISTING OF A MIXTURE OF (A) ABOUT 35 TO 90 WEIGHT PERCENT OF A METAL ORGANO SULFONATE, WHEREIN SAID SULFONATE HAS A MOLECULAR WEIGHT OF FROM ABOUT 300 TO 1200 AND IS SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL AND ALKALI EARTH METAL SULFONATES OF ALKYLATED AROMATIC HYDROCARBONS, (B) ABOUT 10 TO 65 WEIGHT PERCENT OF A CONDENSATE OF A C12-C20 ALIPHATIC ALCOHOL WITH ABOUT 1 TO 4 MOLES OF A C2-C3 ALKYLENE OXIDE PER MOLE OF ALCOHOL AND (C) 0 TO ABOUT 30 WEIGHT PERCENT OF HYDROXYL COMPOUND SELECTED FROM THE GROUP CONSISTING OF GLYCOLS AND GLYCOL ETHERS OF FROM 3 TO 8 CARBON ATOMS AND ALIPHATIC ALCOHOLS OF FROM 3 TO 20 CARBON ATOMS. 